(i) Field of the Invention
The present invention relates to a photosensitive resin composition. More specifically, it relates to a negative type photosensitive resin composition having an excellent sensitivity and resolving properties which can inhibit volume shrinkage at the time of curing, can suitably adhere to a substrate, and can form a polyimide coating film pattern having a good heat-resistance on the substrate by baking.
(ii) Description of the Related Art
Photosensitive polyimides which are heat-resistant photosensitive materials have been widely used as insulating films and passivation films for semiconductors. The well known photosensitive polyimides can be prepared by mixing a polyimide precursor with a compound having a carbon-carbon double bond capable of polymerizing by light irradiation, or chemically bonding the above-mentioned compound to the above-mentioned precursor by an ester linkage. For example, they are disclosed in Japanese Patent Application Laid-open Nos. (Sho)54-145794 and (Hei)2-144539, and Japanese Patent Publication No. (Sho)55-41422. However, for any of these polyimides, it is necessary to introduce a large amount, such as 50% by weight or more, of the compound having the carbon-carbon double bond into the polyimide precursor in order to practically carry out patterning, so that the deterioration of the resolving properties and the large volume shrinkage at curing can be avoided. On the other hand, there has also been suggested a method in which instead of the compound having the carbon-carbon double bond, a compound for generating an acid by light irradiation is used, whereby the above-mentioned problems can be solved. For example, Japanese Patent Application Laid-open No. (Hei)3-763 discloses a method which comprises blending the compound for generating an acid by light irradiation with a polyimide having an acyloxy group, and Japanese Patent Application Laid-open No. (Hei)4-120171 discloses a method which comprises blending the above-mentioned compound with a polyamic acid derivative into which an organic group is introduced by an ester linkage, whereby the formation of a positive type pattern can be achieved. These compositions obtained by these methods have excellent sensitvity and resolution properties can inhibit the volume shrinkage at the time of curing, but the adhesion of them to the substrate is so poor that they are not practical.